Thursday, September 23, 2010

2.9a Secrets of Healthy Food - the Carbohydrates

Physician's Notebooks 2  - - See Homepage

Preface to Food Nutrients:  The following sections have in mind a presentation of the food nutrients - the carbohydrates, lipids, proteins, and vitamins & minerals - first off as chemicals.  This is directed toward student readers who may need to use the knowledge for getting good marks on their tests and winning scholarships and helping initiate professional careers. But also I want it to lead into the functions of food chemicals in good health leading the average reader to healthy longevity, which should be the focus of everyone. Each reader will have his or her own focus they may wish to concentrate memory on.  OK, we start among the Caloric Nutrients with the carbohydrates. Caloric nutrient as the name suggests produce energy calories in contrast to vitamins & minerals which mediate the chemical reactions that produce the calories without being consumed themselves in the reactions.

 2.9a: The Caloric Nutrients - Carbohydrates (Update 02 Dec. 2017). The following are the main topic headings in order in text.
Molecular structure
Carbohydrate is our manna from heaven 
Types of Carbohydrate 
Hyperglycemia & Hypoglycemia 
The Common Food Sugars  
The most common food carbohydrate, starch 
Digestion  & Absorption 
Surviving in a Famine 
Insulin's Role  
Storage in Body 
"Carbohydrate"because molecular structure shows carbohydrates to be made of C (Carbon hence “carbo”), and H2O (water, hence “-hydrate”). The basic units of carbohydrates are sugars. Glucose is the main sugar. All carbohydrates get digested or metabolized down to the basic glucose structure and then it is used mostly to produce energy but also can be used as part of structures. The simplest chemical expression of Glucose is  C6H12O6. It shows the ratio of carbon C, hydrogen H and oxygen O atoms in a single molecule of Glucose.  But Glucose actually exists the 3-D, cyclic structure molecule 
Note the molecule's 6-sided hexagon shape with one atom Oxygen, O, at one of the apexes of the hexagon and atoms of Carbon, C, at all the other apexes (In the above structure, the C's at the other apexes of the hexagon are not shown but should be visualized by the reader).  Also there is a numbering system, not shown above that will help classify the different 1-sugar carbohydrates. Starting at the apex O oxygen atom, you count the carbon atoms in a clockwise direction around the hexagon beginning immediately to your the reader's right with C1 and counting C2, C3, C4, C5 for all the apex C's and then C6 for the CH2OH C atom that juts out of the top of the hexagon to your right.

The structure is important for digestion and for metabolism because the 3-D structure is acted upon by enzymes like key in lock.
   Carbohydrate is our manna from heaven; its ultimate source comes from photosynthesis in green plants: the carbon dioxide (CO2) in Earth's atmosphere is the source of C carbon that is combined with water (H2O) by the energy in our Sun's rays (Photons), the reaction being sped by the enzyme chlorophyll. The full reaction is 
CO2 + H2O + Photons (Chlorophyll)---->Cn(H2O)n (Carbohydrate) + O2.
 At one swoop, the chlorophyll in green leaf converts the sun's ray's energy to produce a basic food substance (carbohydrate), clears the atmosphere of the greenhouse gas CO2 and supplies our breathing oxygen O2.
Types of Carbohydrate: The general structure for carbohydrate is Cn(H2O)n.  Simplest is the sugars that are monosaccharides ("mono-," one or single, and “-saccharide,” sugar), most kinds of which are molecules where the above subscript n is either 6 or 5. In the 6-C sugars “hexose,” the hexose is prefix for the number 6. These are  important in producing the energy from food that allows us to move and function metabolically. The sugar Glucose, whose properties are determined by its 3-D structure (See above), is the most important hexose.
   Hyperglycemia & Hypoglycemia: Glucose in blood when high is hyperglycemia, as seen in diabetes mellitus, and when too low due to a diabetic injecting self with excess insulin is hypoglycemia, which causes cold sweat, fainting and, if prolonged, death. For best body functioning and no unpleasant symptoms, it needs artery blood glucose concentrations between 60 and 120 mg% (3.3 to 6.6 mM/L).
  The Common Food Sugars  Our food also has the 6-C monosaccharide sugar fructose (as name suggests, it is sugar of fruit), and galactose (in milk). The 3 monosaccharides – glucose, fructose, galactose – are molecules that in simple chemical notation are C6H12O6, and each simple monosaccharide differs from other only in 3-D and cyclic structure.
   Food sugars of 2 each monosaccharides are disaccharides (“di” = Greek “two”). Sucrose table sugar is the disaccharide made of a molecule each of glucose and fructose. Maltose sugar of plant stems is disaccharide of 2 linked glucoses, and Lactose sugar of milk is disaccharide of glucose and galactose.
   The most common food carbohydrate, starch, is composed of very large molecules, each molecule of starch consisting of 100's of monosaccharides. This carbohydrate is called “polysaccharide” ("poly-" is the prefix for many, in Englished, multi-). Starches differ from each other in number of monosaccharides, in the branching in the molecule, and in the kind of chemical bonding. The purpose of starches is storage of the energy in food. In humans, the equivalent of starch is glycogen, which is formed and stored in liver, muscle and brain when an excess of glucose gets produced from the diet. Glycogen allows us to go without food for days as a source of internal energy by getting reconverted into glucose and burned as fuel (metaphoric for glucose getting oxidized and releasing its ATP storage packets)
Understanding carbohydrate at level of molecule – from polysaccharide as starch or glycogen, disaccharide as common form of food sugars, and monosaccharide 6-C sugar unit – is key to the digestion and utilization of carbohydrate. We eat the polysaccharides and they get digested quickly in mouth and stomach to the disaccharide sugars, and to fructose, galactose (from milk) and glucose, and these 3 monosaccharides are absorbed into blood and transported to liver, where the galactose and fructose are converted to glucose the final carbohydrate fuel unit. Of course we may also eat di- and mono-saccharides directly with the same final effect to convert to glucose in liver.
Here is where “manna from heaven” comes in. Carbohydrate is the original food substance. Plants form it from air and water, using sun’s energy plus chlorophyll in green leaf. An animal cannot make it from simpler molecules. Most calories we need to move and much of our structural substance comes from the body’s conversion of glucose into energy or into other chemical compounds. So an animal must eat plants or must eat other animals that eat plants to continue to live. From glucose, many other nutrients are made by living things. Many living forms live purely on the carbohydrates, which are closest to a universal food.
There are also 5-carbon sugars called pentoses whose structure is essentially the same as the 6-carbon variety but whose basic units is 5-carbon saccharides. They may be part of enzymes or other structural units. Some genetic disease involve them but in general they are less important than 6-carbons.
   Digestion  & Absorption of starch as for example bread, can start with cutting into small pieces and cooking. Good boiling (15 min with 30-min steep), especially in slightly acid solution (a little vinegar to pot) will start conversion of starch to sugar. The digestion of starch actually starts or continues in mouth as you chew because saliva contains enzyme that breaks down starch molecule to sugar monosaccharides. Chewing slowly and well is good for the digestion.
   In stomach and upper intestine, the carbohydrates - starches and disaccharide food sugars – digest to the 6-C saccharides which can pass thru pores in wall in upper small intestine into venous blood that goes to liver.
    Surviving in a Famine   If you know carbohydrate digestion, it will come in handy in a famine because the most important carbohydrate food is not normally available since we humans – unlike cow and other ruminant – lack ability to digest starch-like cellulose, the structural substance of plants. But, if you recall that a complex carbohydrate can be digested by boiling in slightly acid solution, and apply that by boiling (with a little vinegar if you have it) bark, leaf, grass, and wood that is cut up into very small pieces next time you are caught in a famine, you will be rewarded by getting sweet soup and it will earn you a “Corky” for popping up long after others sink.
   Insulin's Role  With the help of insulin produced by special cells in the pancreas gland, glucose enters cells and either breaks down and combines with oxygen, in a metabolic cycle, to produce phosphate bond packets of energy (ADP to ATP and the ATP releases high energy packet per phosphate bond) to energize the body or else is turned into or combined with structural units of starch, fat or protein.
  To read following is Section B on Lipids now, click
2.9b Fats or Lipids in Foods

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